Although if you have X in circulation as money, and Y in stock market valuation, you could say Y/(X+Y) of total value is in the stock market.
If the market valuation goes up to Y+Z, you could say money has "entered" the stock market, pushing its share of value to (Y+Z)/(X+Y+Z) even though the money in circulation, X, could be unchanged.
If the market valuation goes up to Y+Z, you could say money has "entered" the stock market, pushing its share of value to (Y+Z)/(X+Y+Z) even though the money in circulation, X, could be unchanged.